1. Field of the Invention
This invention relates generally to gas turbines, and more particularly to a single-wheel radial flow gas turbine in which the rotor has a centrifugal compressor and a radial outward flow turbine on the same side of the wheel and in which the stator has a radial flow combustor and nozzle vanes positioned radially between the compressor and the turbine.
2. Description of the Related Art
Industrial gas turbines are commonly employed in applications where high power to weight ratio, low emissions, and high availability requirements prohibit the use of reciprocating engines. For example, in the oil and gas industry, small industrial gas turbines are used for pipeline compression, oil pumping, water injection, gas lift, and offshore platform power generation. Also, in the large electric power plant market, gas turbine combined cycle plants are preferred because of their low air emissions and part load performance. Currently, approximately 40,000 industrial gas turbines are installed throughout the world. U.S. Pat. No. 3,015,211 to Luttrell, which is incorporated herein by reference, is an example of a gas turbine device.
Simple cycle gas turbines consist of three principal components: a compressor, a combustor, and a turbine. The compressor ingests and compresses ambient air, the combustor heats that air by fuel combustion, and the turbine expands the resulting hot air to generate mechanical shaft output power. This open thermodynamic compression-combustion-expansion process is also called the Brayton thermodynamic cycle. Brayton cycle industrial gas turbines are widely used in applications ranging from power generation to gas compression.
Modern small industrial gas turbines are technically complex machines, consisting of multiple rotating parts, bearings, seals, lube oil systems, and sophisticated electronic controls. Most gas turbines above 500 kW output power employ axial compressor and axial turbine design; i.e., the airflow follows primarily along the direction of the axis of the gas turbine shaft. This type of design is a direct evolution from the airplane jet engine and clearly provides the highest aerodynamic efficiency. However, the axial design does not provide lowest weight, small dimensions, portability, or ease of maintanence. As a matter of fact, modern axial flow gas turbines are so technically sophisticated that a user cannot perform even the most basic repairs, diagnostics, and trouble shooting without the gas turbine manufacturer's participation. Additionally, although they are optimized for highest efficiency, most modern gas turbines do not allow use of a wide range of fuels and cannot handle severe environmental conditions. Portability, fuel flexibility, and ruggedness are sacrificed for efficiency. While this may be desirable for most permanently installed large power plant applications, it is not practical for small portable power generation applications.
For smaller power applications (for instance, less than about 500 kW), existing gas turbines often employ a centrifugal compressor, a 180° flow turning combustor, and a radial inflow turbine. Such gas turbines are often called radial flow or centrifugal turbines. Such conventional radial flow gas turbines are more compact than axial flow gas turbines, but because of their 180° flow turning combustors, they are very complex and expensive to manufacture and they are somewhat intolerant to rugged environmental operating conditions.
For a number of industrial applications, customers desire simple, low cost gas turbines that can function under very rugged environmental conditions, are easy to repair or replace, can be operated by personnel with minimal training, are portable, and can handle a wide variety of fuel sources. Such applications include upstream oil production and military power generation. Thus, a need currently exists for a lightweight, small, portable, and rugged gas turbine that can provide a very simple power generation alternative. It would be a significant advancement in the art to provide a gas turbine that incorporates only one rotating part and has no lube oil or sealed gas requirements so that manufacturing, maintenance, repair, and replacement costs are low. Such a design would be highly portable, able to operate in rugged environments on a wide range of fuels, and tolerant of ingestion of large particle matter such as sand or dirt.